1. Field of the Invention
The present invention relates generally to implants and, more particularly, to biomedical balloons and applications employing such balloons.
2. Description of Related Art
Balloon catheters have been employed in angioplasty applications for many years. A catheter having an inflatable balloon formed therein may be inserted into an artery percutaneously, and the balloon guided to a treatment area. The balloon may then be inflated in order to mitigate the effect of plaque deposits in, for example, a coronary artery. In some cases a balloon catheter is employed to implant a stent into an artery of a patient in order to decrease the likelihood of a recurrence of arterial blockage. Balloon catheters used in angioplasty are commonly removed from the patient after use as a result of, for example, typically being meant only to temporarily inflate the vessel or temporarily block the vessel for delivery of a stent or drugs. Additionally, removal of the balloon is typically necessary in order to attenuate complications that may arise pertaining, for example, to long-term effects which may stem from contact between a material of the balloon and the patient's tissue.
Balloon devices have found utility in biomedical areas other than cardiovascular applications. For example, balloons may be used in kyphoplasty applications wherein the effect of a vertebral fracture from osteoporosis is treated by inserting a balloon into a cavity formed in the fracture. Inflating the balloon may cause pieces of the fracture to return to a positions or orientations approximating those existing before for example a traumatic event that caused the fracture. Bone cement may then be inserted into the cavity in order to stabilize the bone fragments. In other vertebroplasty applications, bone cement may be inserted into, for example, cavities formed in weakened or fractured bones in order to provide enhanced strength and stability.
Unfortunately, cement extravasation can be a problem in these kyphoplasty and vertebroplasty situations. For instance, cement inserted into bone may extrude into surrounding tissues and nerves, causing pain and other complications. One way to prevent cement extravasation is to insert a balloon into the treatment cavity, fill the balloon with bone cement, and allow the cement to harden inside the balloon while the balloon remains in the body of the patient. Such a solution may not always be viable due for example to confounding factors such as situations wherein the presence of the balloon may prevent bonding between the bone cement and the bone tissue of interest. Consequently, gaps may form between an outer surface of the balloon and surrounding bone, introducing for example attendant risks of infection, bone loss, and pain.
A need thus exists in the prior art for a method of preventing cement extravasation in vertebroplasty and kyphoplasty applications. A further need exists for enabling bonding between bone cement and bone tissue following vertebroplasty and kyphoplasty treatments.
A medicinal substance can be administered to a patient systemically or locally. A systemically administered medicinal substance enters into the blood stream, travels throughout the body, and, preferentially, reaches the part of the patient's body in need of treatment at an effective dose before being degraded by metabolism and excreted. The systemic administration of medicinal substances can be achieved by oral application (e.g., syrups, tablets, capsules and the like), needle injection, transdermal delivery (e.g., a medicinal substance incorporated into a skin patch), and subdermal delivery (e.g., a medicinal substance formulation in a metabolizable matrix placed beneath the skin to release, for example, nicotine or birth control drugs). Systemically delivered medicinal substances can be inefficient when only a small amount of the administered dose reaches the site sought for therapeutic action. Moreover, with systemic delivery a medicinal substance can enter parts of the body where it can actually do harm or produce a noxious side effect.
Medicinal substances can be delivered locally by injection (e.g., injection of anesthetic into a patient's gums) or topically (e.g., creams, ointments, and sprays). Although the local delivery of medicinal substances can in some instances overcome problems of dilution and migration associated with systemic administration, multiple injections may be required to achieve or sustain a therapeutically effective dose over time. To avoid a need for multiple injections, a therapeutic agent may be delivered locally by way of a timed-released or controlled delivery type device. In many cases, timed-released devices are formed as a mixture or dispersion of the therapeutic agent in a degrading or non-degrading delivery material or vehicle. In some cases the therapeutic agent is destroyed, denatured, or looses its activity when combined with the delivery vehicle or material. In other cases, controlled delivery devices rely on diffusion of the therapeutic agent from the delivery material or vehicle, but the therapeutic agent may be too large to diffuse through a delivery material matrix of the controlled delivery device at a reasonable rate. In cases where the volume of the therapeutic time-released agent is large, an open procedure may be required to insert a relatively large therapeutic time-release device to the desired anatomical location. To avoid an open procedure for the delivery of a large volume of therapeutic agent, many small devices may be inserted, such as microspheres. The microspheres, however, may be difficult to retrieve if there is a complication. Even when local delivery of medicinal substances to a target site is possible, an important consideration still remains of maximizing the therapeutic effectiveness of the local drug delivery by controlling the proper dose and duration of the local delivery of the medicinal substance.
A need thus exists in the prior art for a delivery method or apparatus that can avoid undesirable activity losses of a therapeutic agent that may be associated with techniques that combine the therapeutic agent with a delivery material or vehicle. A further need exists for a method or apparatus that can avoid a requirement of diffusion of a therapeutic agent through a material of a delivery device. A still further need exists for methods or apparatus that may not require implantation of multitudes of small delivery devices and/or associated problems that may be presented of having to retrieve those small devices from an anatomical location upon the occurrence of complications, as well as methods or apparatus that may not require open surgical procedures for delivering large amounts of therapeutic agents.